JP2009284668A - Power supply system and vehicle with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply system that improves the efficiency of overall energy, while reliably preventing an excessive current from passing, and to provide a vehicle with the same. <P>SOLUTION: A converter ECU 2 switches a control mode of each converter 8-1, 8-2 between a non-step-up mode that each converter stops voltage conversion operation and a step-up mode that at least one converter executes voltage conversion operation. When a request for switching from the step-up mode to the non-step-up mode is generated, the converter ECU 2 stops the converter corresponding to an energy storage part having a higher charge/discharge voltage while making the converter corresponding to an energy storage part having a lower charge/discharge voltage execute step-down operation in accordance with a state that a difference of the charge/discharge voltage between the energy storage parts is larger than a reference voltage. In the step-down operation, the converter ECU 2 increases an ON-duty of an upper arm, but reduces a carrier frequency when the ON-duty reaches a maximum value of the ON-duty that the ON-duty is not affected by dead time. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power supply system and a vehicle including the same, and more specifically to a power supply system including a plurality of power storage units and a vehicle including the same.

  In recent years, in consideration of environmental problems, vehicles using an electric motor as a driving force source such as an electric vehicle, a hybrid vehicle, and a fuel cell vehicle have attracted attention. Such a vehicle is equipped with a power storage unit composed of a secondary battery, an electric double layer capacitor, or the like in order to supply electric power to an electric motor or to convert kinetic energy into electric energy and store it during regenerative braking. ing.

  In a vehicle using such an electric motor as a driving force source, it is desirable to increase the charge / discharge capacity of the power storage unit in order to improve traveling performance such as acceleration performance and traveling distance. As a method for increasing the charge / discharge capacity of the power storage unit, a configuration in which a plurality of power storage units is mounted has been proposed.

For example, JP-A-9-233710 (Patent Document 1) discloses a charge / discharge device for forming a storage battery used for charge / discharge when forming a storage battery. This charging / discharging device includes a charging rectifier circuit that rectifies an AC power source, and a regenerative rectifier circuit that is connected in reverse parallel to the charging rectifier circuit and regenerates the amount of electricity of the divided storage battery to the AC power source. And a plurality of buck-boost converters provided between the charging rectifier circuit and the divided storage battery.
JP-A-9-233710 JP 2006-187186 A

  Here, as a step-up / down converter, as disclosed in Japanese Patent Laid-Open No. 9-233710 (Patent Document 1), two switching elements connected in series between a power supply line and a ground line, and one end Is generally connected to a midpoint between two switching elements, and includes a chopper circuit including a reactor having the other end connected to a power supply line of a power supply. In this configuration, by turning on and off the two switching elements at a predetermined duty ratio, the DC voltage from the power supply is boosted during discharging, while the DC power received from the power supply line and the earth line is stepped down during charging. Can do.

  On the other hand, depending on the power required for the power supply system, there may occur a situation where the loss of the buck-boost converter cannot be ignored when the buck-boost converter is operated to realize the required power. That is, the smaller the required power, the more likely the loss of the buck-boost converter becomes relatively large.

  The loss of the buck-boost converter can be effectively suppressed by stopping the buck-boost converter, for example, when the required power is small. However, in the charging / discharging device disclosed in Japanese Patent Application Laid-Open No. 9-233710 (Patent Document 1), the charging / discharging of each storage battery is individually controlled by the corresponding step-up / down converter, and therefore the charging / discharging voltage between the storage batteries. Differences can occur. Therefore, when all of the plurality of step-up / step-down converters are stopped, according to this difference, an excessive current flows from the power storage unit having a relatively high charge / discharge voltage toward the power storage unit having a relatively low charge / discharge voltage. There is a possibility of flowing. As a result, the battery characteristics of the storage battery are deteriorated, or the switching element constituting the buck-boost converter is damaged, which can lead to a problem that the running performance of the vehicle is restricted.

  Therefore, the present invention has been made to solve such a problem, and an object of the present invention is to provide a power supply system capable of improving the overall energy efficiency while reliably suppressing the passage of an excessive current. It is to provide a vehicle equipped with it.

  According to an aspect of the present invention, a power supply system includes a plurality of power storage units each configured to be chargeable / dischargeable. The power supply system is provided between a power line pair configured to be able to exchange power between the load device and the power supply system, and between the plurality of power storage units and the power line pair, each of which has a corresponding power storage unit and power line pair. A plurality of voltage conversion units that perform a voltage conversion operation between them, and a control device that controls the voltage conversion operations in the plurality of voltage conversion units. Each of the plurality of voltage conversion units includes first and second switching elements connected in series between the power line pair, and performs a voltage conversion operation by a switching operation of the first and second switching elements. The control device includes: a first control mode for controlling the plurality of voltage conversion units so that each of the plurality of voltage conversion units stops the voltage conversion operation; and at least one of the plurality of voltage conversion units performs the voltage conversion operation. The mode setting means for setting to any one of the second control modes to be controlled, and the plurality of voltage converters set to the second control mode are switched to the first control mode by the mode setting means. The voltage conversion control means for stopping the voltage conversion operation in the plurality of voltage conversion units in response to the voltage difference between the charge and discharge voltages being below a predetermined reference value. The voltage conversion control means outputs the voltage from the first power storage unit having a relatively high charge / discharge voltage among the plurality of power storage units directly to the power line pair when the voltage difference is equal to or greater than a predetermined reference value. In this manner, the voltage conversion operation in the corresponding voltage conversion unit is stopped, and the second power storage unit having a relatively low charge / discharge voltage among the plurality of power storage units is charged with the voltage from the first power storage unit. Thus, a voltage difference reducing means for controlling the step-down operation in the corresponding voltage converter is included. The voltage difference reducing means sets the carrier frequency for controlling the switching operation of the first and second switching elements to the first frequency in the voltage conversion unit corresponding to the second power storage unit, A first switching command generating means for increasing a first on-duty which is a ratio of a control cycle length determined by the frequency and an on-period length of the first switching device; and first and second switching devices based on the control cycle length A value obtained by dividing the effective control cycle length obtained by subtracting the dead time during which both are turned off by the control cycle length is preset as the maximum on-duty, and the first on-duty is set to the maximum on-duty in the first switching command generation means. The second switching finger that lowers the carrier frequency from the first frequency. And a generation means.

  Preferably, each of the plurality of voltage conversion units further includes an inductor connected to a connection point between the first switching element and the second switching element. The second switching command generation means lowers the carrier frequency using the second frequency lower than the first frequency as the lower limit frequency. The second frequency is set such that the current flowing through the inductor has a current value that can maintain the core of the inductor in the magnetic unsaturation.

  Preferably, the mode setting means sets the plurality of voltage converters to the first control mode when the required power for the power supply system of the load device falls below a predetermined threshold.

  Preferably, the load device includes a driving force generation unit that receives electric power supplied from the power supply system via the power line pair and generates a driving force of the vehicle. The mode setting means sets the plurality of voltage conversion units to the first control mode when the vehicle is stopped.

  According to another aspect of the present invention, a vehicle includes a power supply system that includes a plurality of power storage units each configured to be chargeable / dischargeable, and a driving force that receives power supplied from the power supply system and generates a driving force. A generator. The power supply system is provided between a power line pair configured to be able to exchange power between the driving force generation unit and the power supply system, and between the plurality of power storage units and the power line pair, each of which corresponds to a corresponding power storage unit and power line. A plurality of voltage conversion units that perform a voltage conversion operation between the pair, and a control device that controls the voltage conversion operations in the plurality of voltage conversion units. Each of the plurality of voltage conversion units includes first and second switching elements connected in series between the power line pair, and performs a voltage conversion operation by a switching operation of the first and second switching elements. The control device includes: a first control mode for controlling the plurality of voltage conversion units so that each of the plurality of voltage conversion units stops the voltage conversion operation; and at least one of the plurality of voltage conversion units performs the voltage conversion operation. The mode setting means for setting to any one of the second control modes to be controlled, and the plurality of voltage converters set to the second control mode are switched to the first control mode by the mode setting means. The voltage conversion control means for stopping the voltage conversion operation in the plurality of voltage conversion units in response to the voltage difference between the charge and discharge voltages being below a predetermined reference value. The voltage conversion control means outputs the voltage from the first power storage unit having a relatively high charge / discharge voltage among the plurality of power storage units directly to the power line pair when the voltage difference is equal to or greater than a predetermined reference value. In this manner, the voltage conversion operation in the corresponding voltage conversion unit is stopped, and the second power storage unit having a relatively low charge / discharge voltage among the plurality of power storage units is charged with the voltage from the first power storage unit. Thus, a voltage difference reducing means for controlling the step-down operation in the corresponding voltage converter is included. The voltage difference reducing means sets the carrier frequency for controlling the switching operation of the first and second switching elements to the first frequency in the voltage conversion unit corresponding to the second power storage unit, A first switching command generating means for increasing a first on-duty which is a ratio of a control cycle length determined by the frequency and an on-period length of the first switching device; and first and second switching devices based on the control cycle length A value obtained by dividing the effective control cycle length obtained by subtracting the dead time during which both are turned off by the control cycle length is preset as the maximum on-duty, and the first on-duty is set to the maximum on-duty in the first switching command generation means. The second switching finger that lowers the carrier frequency from the first frequency. And a generation means.

  According to the present invention, it is possible to realize a power supply system capable of improving the overall energy efficiency and a vehicle including the power supply system while reliably suppressing an excessive current from passing therethrough.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

  FIG. 1 is a schematic configuration diagram showing a main part of a vehicle 100 including a power supply system 1 according to an embodiment of the present invention.

  With reference to FIG. 1, in the present embodiment, a case where driving force generation unit 3 that generates a driving force of vehicle 100 is used as a load device is illustrated. The vehicle 100 travels by transmitting a driving force generated by electric power supplied from the power supply system 1 to the driving force generator 3 to wheels (not shown). In addition, the vehicle 100 generates electric power from kinetic energy by the driving force generator 3 and collects it in the power supply system 1 during regeneration.

  In the present embodiment, power supply system 1 including two power storage units as a plurality of power storage units will be described. Power supply system 1 transmits and receives DC power to and from driving force generator 3 via main positive bus MPL and main negative bus MNL. In the following description, the power supplied from the power supply system 1 to the driving force generator 3 is also referred to as “driving power”, and the power supplied from the driving force generator 3 to the power supply system 1 is also referred to as “regenerative power”. Call it.

  The driving force generator 3 includes a first inverter (INV1) 30-1, a second inverter (INV2) 30-2, a first motor generator (MG1) 34-1 and a second motor generator (MG2) 34-. 2 and a drive ECU (Electrical Control Unit) 32.

  Inverters 30-1 and 30-2 are connected in parallel to main positive bus MPL and main negative bus MNL, and each exchange power with power supply system 1. That is, inverters 30-1 and 30-2 convert driving power (DC power) received via main positive bus MPL and main negative bus MNL into AC power and supply it to motor generators 34-1 and 34-2. On the other hand, AC power generated by the motor generators 34-1 and 34-2 is converted into DC power and supplied to the power supply system 1 as regenerative power. Inverters 30-1 and 30-2 are configured by bridge circuits including switching elements for three phases, for example, and perform switching (circuit opening / closing) operations according to switching commands PWM 1 and PWM 2 received from drive ECU 32, respectively. To generate three-phase AC power.

  Motor generators 34-1 and 34-2 can generate rotational driving force by receiving AC power supplied from inverters 30-1 and 30-2, respectively, and can generate electric power by receiving rotational driving force from the outside. Configured. As an example, motor generators 34-1 and 34-2 are three-phase AC rotating electric machines including a rotor in which permanent magnets are embedded. Motor generators 34-1 and 34-2 are coupled to power transmission mechanism 36, respectively, and transmit the generated driving force to wheels (not shown) by driving shaft 38.

  When driving force generator 3 is applied to a hybrid vehicle, motor generators 34-1 and 34-2 are also connected to an engine (not shown) via power transmission mechanism 36 or driving shaft 38. Control is executed by drive ECU 32 so that the drive force generated by the engine and the drive force generated by motor generators 34-1 and 34-2 have an optimal ratio. When applied to such a hybrid vehicle, the motor generator 34-1 can function exclusively as a generator, and the motor generator 34-2 can function exclusively as an electric motor.

  The drive ECU 32 executes a program stored in advance, so that the motor generator 34-is based on a signal transmitted from each sensor (not shown), a traveling state, a change rate of the accelerator opening, a stored map, and the like. Torque target values TR1, TR2 and rotation speed target values MRN1, MRN2 of 1,34-2 are calculated. Then, drive ECU 32 generates switching commands PWM1 and PWM2 so that the generated torque and rotation speed of motor generators 34-1 and 34-2 become torque target values TR1 and TR2 and rotation speed target values MRN1 and MRN2, respectively. To control the inverters 30-1 and 30-2. Further, drive ECU 32 outputs calculated torque target values TR1, TR2 and rotation speed target values MRN1, MRN2 to power supply system 1. If torque target values TR1 and TR2 when motor generators 34-1 and 34-2 generate rotational driving force are positive values, torque target values TR1 and TR2 are negative values during regenerative braking.

(Power system configuration)
The power supply system 1 includes a smoothing capacitor C, an input / output current detection unit 16, an input / output voltage detection unit 18, a first converter (CONV1) 8-1, a second converter (CONV2) 8-2, Power storage unit 6-1, second power storage unit 6-2, charge / discharge current detection units 10-1, 10-2, charge / discharge voltage detection units 12-1, 12-2, and temperature detection unit 14-1 14-2, converter ECU 2 and battery ECU 4.

  Smoothing capacitor C is connected between main positive bus MPL and main negative bus MNL, and is included in the driving power output from converters 8-1 and 8-2 and the regenerative power supplied from driving force generator 3. Reduce fluctuation components.

  The input / output current detection unit 16 is inserted into one of the main positive bus MPL and the main negative bus MNL, and calculates the input / output current values Ih of the driving power and the regenerative power exchanged with the driving force generation unit 3. The detection result is output to converter ECU 2.

  The input / output voltage detector 18 is connected between the main positive bus MPL and the main negative bus MNL, and detects an input / output voltage value Vh of driving power and regenerative power exchanged with the driving force generator 3. The detection result is output to converter ECU 2.

  Converters 8-1 and 8-2 are provided between main positive bus MPL and main negative bus MNL and power storage units 6-1 and 6-2, respectively. Power conversion operation is performed between bus MPL and main negative bus MNL. Specifically, converters 8-1 and 8-2 boost the discharge power from power storage units 6-1 and 6-2 to a predetermined voltage and supply it as drive power, while supplying from drive force generation unit 3. The regenerative power that is generated is stepped down to a predetermined voltage to charge power storage units 6-1 and 6-2. As an example, converters 8-1 and 8-2 are configured by a step-up / down chopper circuit.

  Power storage units 6-1 and 6-2 are connected in parallel to main positive bus MPL and main negative bus MNL via converters 8-1, 8-2, respectively. As an example, power storage units 6-1 and 6-2 include a secondary battery configured to be chargeable / dischargeable, such as a nickel hydride or lithium ion battery, or an electric double layer capacitor. In the present embodiment, power storage unit 6-1 and power storage unit 6-2 are configured to have the same power supply voltage.

  Charging / discharging current detection units 10-1 and 10-2 are inserted in one power line connecting power storage units 6-1 and 6-2 and converters 8-1 and 8-2, respectively, and power storage unit 6-1. , 6-2 are detected and charging / discharging current values Ib1, Ib2 used for charging / discharging are detected, and the detection results are output to the battery ECU 4.

  Charging / discharging voltage detection units 12-1 and 12-2 are connected between power lines connecting power storage units 6-1 and 6-2 and converters 8-1 and 8-2, respectively. -2 charge / discharge voltage values Vb1 and Vb2 are detected, and the detection result is output to the battery ECU 4.

  The temperature detectors 14-1 and 14-2 are disposed close to the battery cells and the like constituting the power storage units 6-1 and 6-2, respectively, and are stored in the power storage units 6-1 and 6-2. The part temperatures Tb1, Tb2 are detected, and the detection results are output to the battery ECU 4. The temperature detection units 14-1 and 14-2 are averaged based on the detection results of the plurality of detection elements arranged in association with the plurality of battery cells constituting the power storage units 6-1 and 6-2, respectively. It is also possible to configure so that the representative value is output by a conversion process or the like.

  Battery ECU 4 includes charge / discharge current values Ib1, Ib2 received from charge / discharge current detectors 10-1, 10-2, charge / discharge voltage values Vb1, Vb2, received from charge / discharge voltage detectors 12-1, 12-2, Based on power storage unit temperatures Tb1 and Tb2 received from temperature detection units 14-1 and 14-2, charge states SOC1 and SOC2 (SOC: State Of Charge) in power storage units 6-1 and 6-2 are calculated. To do. Since various well-known techniques can be used for the configuration for calculating the SOC of power storage units 6-1 and 6-2, detailed description will be omitted.

  Further, battery ECU 4 derives allowable power (charge allowable power Win1, Win2 and discharge allowable power Wout1, Wout2) based on derived SOC1 and SOC2 of power storage units 6-1 and 6-2. Charge allowable power Win1, Win2 and discharge allowable power Wout1, Wout2 are short-term limit values of charge power and discharge power at each time point, which are defined by their chemical reaction limits.

  Then, battery ECU 4 outputs derived SOCs 1, SOC 2, charge allowable power Win 1, Win 2 and discharge allowable power Wout 1, Wout 2 of power storage units 6-1, 6-2 to converter ECU 2.

  Converter ECU 2 receives input / output current value Ih received from input / output current detector 16, input / output voltage value Vh received from input / output voltage detector 18, and charge / discharge current detectors 10-1 and 10-2. Charge / discharge current values Ib1, Ib2, charge / discharge voltage values Vb1, Vb2 received from charge / discharge voltage detectors 12-1, 12-2, Win1, Win2, Wout1, Wout2 received from battery ECU 4, and drive ECU 32 Based on torque target values TR1 and TR2 and rotation speed target values MRN1 and MRN2 received from, switching commands PWC1 and PWC2 are generated according to a control structure to be described later, and converters 8-1 and 8-2 are controlled.

FIG. 2 is a schematic configuration diagram of converters 8-1 and 8-2 according to the embodiment of the present invention.
Referring to FIG. 2, converter 8-1 includes a chopper circuit 40-1 and a smoothing capacitor C1.

  Chopper circuit 40-1 boosts DC power (drive power) received from power storage unit 6-1 during discharging in response to switching command PWC1 from converter ECU 2 (FIG. 1), while main positive bus MPL and The DC power (regenerative power) received from the main negative bus MNL is stepped down. Chopper circuit 40-1 includes a positive bus LN1A, a negative bus LN1C, a wiring LN1B, transistors Q1A and Q1B as switching elements, diodes D1A and D1B, and an inductor L1.

  Positive bus LN1A has one end connected to the collector of transistor Q1B and the other end connected to main positive bus MPL. Negative bus LN1C has one end connected to the negative side of power storage unit 6-1 and the other end connected to main negative bus MNL.

  Transistors Q1A and Q1B are connected in series between negative bus LN1C and positive bus LN1A. Transistor Q1A has an emitter connected to negative bus LN1C, and transistor Q1B has a collector connected to positive bus LN1A. Further, diodes D1A and D1B that flow current from the emitter side to the collector side are connected between the collector and emitter of the transistors Q1A and Q1B, respectively. Further, inductor L1 is connected to a connection point between transistor Q1A and transistor Q1B.

  Wiring LN1B has one end connected to the positive side of power storage unit 6-1 and the other end connected to inductor L1.

  Smoothing capacitor C1 is connected between wiring LN1B and negative bus LN1C, and reduces the AC component included in the DC voltage between wiring LN1B and negative bus LN1C.

  Hereinafter, the voltage conversion operation (step-up operation and step-down operation) of converter 8-1 will be described.

  During the boosting operation, converter ECU 2 (FIG. 1) turns on / off transistor Q1A and transistor Q1B at a predetermined duty ratio. In the on period of transistor Q1A, the discharge current flows from power storage unit 6-1 to main positive bus MPL through wiring LN1B, inductor L1, diode D1B, and positive bus LN1A in this order. At the same time, a pump current flows from power storage unit 6-1 through wiring LN1B, inductor L1, transistor Q1A, and negative bus LN1C in this order. The inductor L1 accumulates electromagnetic energy by this pump current. Subsequently, when the transistor Q1A transitions from the on state to the off state, the inductor L1 superimposes the accumulated electromagnetic energy on the discharge current. As a result, the average value of the DC power supplied from converter 8-1 to main positive bus MPL and main negative bus MNL depends on the on-duty of transistor Q1A (which means the period during which transistor Q1A is on). The voltage is boosted by a voltage corresponding to the electromagnetic energy accumulated in L1.

  On the other hand, during the step-down operation, converter ECU 2 turns on / off transistor Q1A and transistor Q1B at a predetermined duty ratio. In the on-period of transistor Q1B, the charging current flows from main positive bus MPL through positive bus LN1A, transistor Q1B, inductor L1, and wiring LN1B in order to power storage unit 6-1. Subsequently, when the transistor Q1B transitions from the on state to the off state, a magnetic flux is generated so that the inductor L1 prevents a change in current. Therefore, the charging current continues to flow through the diode D1A, the inductor L1, and the wiring LN1B in order. On the other hand, from the viewpoint of electromagnetic energy, since the DC power is supplied only through the main positive bus MPL and the main negative bus MNL only during the ON period of the transistor Q1B, the charging current is kept constant. (Assuming that the inductance of inductor L1 is sufficiently large), the average voltage of the DC power supplied from converter 8-1 to power storage unit 6-1 is changed to the DC voltage between main positive bus MPL and main negative bus MNL by transistor Q1B. Multiplied by an on-duty (meaning a period during which the transistor Q1B is on).

  In order to control such voltage conversion operation of converter 8-1, converter ECU 2 includes switching command PWC1A for controlling on / off of transistor Q1A and switching command PWC1B for controlling on / off of transistor Q1B. PWC1 is generated.

  Since transistor Q1A and transistor Q1B are connected in series between negative bus LN1C and positive bus LN1A, it is necessary to prevent transistors Q1A and Q1B from being turned on simultaneously. Therefore, converter ECU 2 provides switching commands PWC1A and PWC1B with a dead time for preventing transistors Q1A and Q1B from being turned on simultaneously. This dead time is set in advance to a predetermined time based on the element characteristics of the transistors Q1A and Q1B.

  Since converter 8-2 has the same configuration and operation as converter 8-1 described above, detailed description will not be repeated.

  Hereinafter, the control structure in converter ECU 2 will be described in detail. Converter ECU 2 executes the same control for both driving power and regenerative power, but in this embodiment, a control structure for driving power is described as an example in order to facilitate understanding. To do.

  FIG. 3 is a block diagram for realizing generation of a switching command (step-up operation) in converter ECU 2.

  Referring to FIG. 3, converter ECU 2 includes a mode determination unit 20, a control unit 22, a first switching command generation unit 24, and a second switching command generation unit 26.

  The mode determination unit 20 is configured to convert the converters 8-1 and 8-based on the driving power (hereinafter also referred to as required power) PR and the vehicle speed V requested by the driving force generation unit 3 (FIG. 1) to the power supply system 1. 2 determines the control mode. The required power PR and the vehicle speed V are sent from the host ECU or various sensors as signals representing the traveling state of the vehicle 100.

  Specifically, “boost mode” and “non-boost mode” are set in advance as control modes in converters 8-1 and 8-2. The “boost mode” is a mode in which at least one of converters 8-1 and 8-2 performs a boost operation. In other words, in the boost mode, one converter boost mode in which one of converters 8-1 and 8-2 performs a boost operation and the other is stopped, and both converters 8-1 and 8-2 are boost operations. And a two-converter boost mode. In contrast, the “non-boosting mode” is a mode in which both converters 8-1 and 8-2 stop the boosting operation.

  When mode determination unit 20 determines a control mode in converters 8-1 and 8-2 based on the running state of vehicle 100, mode determination unit 20 outputs signal MD representing the determined control mode to control unit 22.

  When control unit 22 receives signal MD from mode determination unit 20, control unit 22 generates signal CTL1 for controlling the operation state and stop state of converter 8-1 according to the control structure described later, in accordance with the determined control mode. The generated signal CTL1 is output to the first switching command generator 24.

  Control unit 22 generates signal CTL2 for controlling the operation state and stop state of converter 8-2 in accordance with the control structure described later according to the determined control mode, and generates the generated signal CTL2 as the second signal CTL2. Output to the switching command generator 26.

  In accordance with signal CTL1 from controller 22, first switching command generator 24 switches switching command PWC1A for controlling on / off of transistor Q1A and switching command PWC1B for controlling on / off of transistor Q1B according to a control structure described later. A switching command PWC1 is generated.

  In accordance with signal CTL2 from control unit 22, second switching command generation unit 26 switches switching command PWC2A for controlling on / off of transistor Q2A and switching command PWC2B for controlling on / off of transistor Q2B according to a control structure described later. A switching command PWC2 is generated.

  As described above, in the present embodiment, converter ECU 2 switches the control mode for converters 8-1 and 8-2 between the boosting mode and the non-boosting mode according to the traveling state of vehicle 100. Thereby, the magnitude of the electric power taken out from power storage units 6-1 and 6-2 corresponding to converters 8-1 and 8-2 is controlled.

  FIG. 4 is a flowchart for illustrating the operation of determining the control mode of the converter in converter ECU 2.

  Referring to FIG. 4, when the process is started, mode determination unit 20 determines whether vehicle 100 is in a stopped state based on vehicle speed V received from the vehicle speed sensor (step S01).

  When vehicle 100 is in a stopped state (YES in step S01), mode determination unit 20 determines the control mode of converters 8-1, 8-2 to the non-boosting mode (step S04).

  On the other hand, when vehicle 100 is not in a stopped state (NO in step S01), mode determination unit 20 further determines whether or not required power PR is smaller than first threshold value Pth1 (step S02). The first threshold Pth1 is set to the maximum power that can be supplied from the power supply system 1 when driving the driving force generator 3 without boosting the output voltage from the power storage units 6-1 and 6-2. . The first threshold value Pth1 is obtained in advance by experiments and stored in the mode determination unit 20.

  When required power PR is smaller than first threshold value Pth1 (YES in step S02), mode determining unit 20 determines the control mode of converters 8-1, 8-2 to the non-boosting mode (step). S04).

  On the other hand, when required power PR is equal to or higher than first threshold value Pth1 (NO in step S02), mode determination unit 20 sets the control mode of converters 8-1, 8-2 to the boost mode. (Step S03).

  Although illustration is omitted, in steps S03 and after, converters 8-1, 8-2 have one converter boost mode in which only one performs a boost operation according to the magnitude of required power PR, and both perform boost operation. Control is made to one of the two converter boost modes to be performed.

  Specifically, when the required power PR is equal to or higher than the second threshold Pth2 higher than the first threshold Pth1, the electric power supplied from the power storage units 6-1 and 6-2 to the driving force generation unit 3 Converters 8-1 and 8-2 are controlled so that the total value becomes required power PR (two-converter boost mode). The second threshold value Pth2 is set to the discharge allowable power Wout of the power storage unit having a small absolute value of the discharge allowable power Wout among the power storage units 6-1 and 6-2.

  Further, when the required power PR is equal to or higher than the first threshold value Pth and smaller than the second threshold value Pth2, the converters 8-1, 8-2 are switched and operated to thereby convert the converters 8-1, 8-2. One of -2 is boosted and the other is stopped (1 converter boost mode). At this time, the boost operation of one converter is controlled so that the power supplied from the corresponding power storage unit to the driving force generation unit 3 becomes the required power PR.

  As apparent from FIG. 4, in the present embodiment, converter ECU 2 provides converters 8-1, 8-2 when vehicle 100 is in a stopped state or when required power PR is smaller than first threshold value Pth 1. The step-up operation in is stopped. FIG. 5 is a diagram for illustrating the states of converters 8-1 and 8-2 in the non-boosting mode.

  Referring to FIG. 5, in the non-boosting mode, converter ECU 2 keeps transistor Q1B of converter 8-1 off, while keeping transistor Q1B on (that is, the on-duty of transistor Q1B is set to “1”). ").

  Further, converter ECU 2 keeps transistor Q2A of converter 8-2 off, while keeping transistor Q2B on (that is, the on-duty of transistor Q2B is set to “1”).

  Thus, converters 8-1 and 8-2 function as simple wirings for electrically connecting power storage units 6-1 and 6-2 to main positive bus MPL and main negative bus MNL. . That is, power storage unit 6-1 and power storage unit 6-2 are equivalent to a state in which they are completely connected in parallel to main positive bus MPL and main negative bus MNL (hereinafter, also simply referred to as “completely parallel state”). . Therefore, the loss generated in each of converters 8-1, 8-2 is suppressed by the loss (switching loss) generated during the switching operation of transistors Q1A, Q1B (or Q2A, Q2B), and diode D1B (or D2B). ) And the conduction loss of the transistor Q1B (or Q2B). As a result, the conversion loss in converters 8-1, 8-2 can be suppressed, so that the overall energy efficiency can be increased.

  Therefore, in the present embodiment, as described with reference to FIG. 4, when required power PR is relatively small or when vehicle 100 is in a stopped state, converters 8-1 and 8-2 are positively activated in boost mode. By switching from to the non-boosting mode, the overall energy efficiency can be improved.

  Further, by setting converters 8-1 and 8-2 to the non-boosting mode when vehicle 100 is in a stopped state, noise generated by the switching operation of the transistor, which becomes more prominent when the vehicle is stopped than when the vehicle is running, is reduced. Can be suppressed. Thereby, the quietness of the vehicle 100 can be improved.

  However, when switching converters 8-1 and 8-2 from the boosting mode to the non-boosting mode, the boosting operation in converters 8-1 and 8-2 is immediately stopped according to the running state of vehicle 100, and power storage unit 6 −1, 6-2 are in a completely parallel state, the moment between the power storage unit 6-1 and the power storage unit 6-2 is instantaneous according to the voltage difference of the charge / discharge voltage between the power storage units 6-1 and 6-2. In particular, an excessive current may flow.

  Specifically, during the step-up mode, the boosting operation in converters 8-1 and 8-2 is individually controlled, so that charging / discharging voltage Vb 1 of power storage unit 6-1 and charging / uncharging of power storage unit 6-2 are performed. There is a considerable voltage difference ΔVb (= | Vb1−Vb2 |) between the discharge voltage Vb2. Therefore, if the vehicle 100 is immediately switched from the boosting mode to the non-boosting mode in response to the stop state, the charging / discharging voltage is relatively increased from the power storage unit having a relatively high charging / discharging voltage at the switching timing. An excessive current corresponding to the voltage difference ΔVb passes toward the lower power storage unit. As a result, the power storage units 6-1 and 6-2 may be overheated and the battery performance may be deteriorated, or the internal fuse may be damaged. Also, there are power lines connecting main positive bus MPL, main negative bus MNL to converters 8-1, 8-2 to power storage units 6-1 and 6-2, transistors constituting converters 8-1, 8-2, and the like. There is a risk of thermal destruction.

  Therefore, in power supply system 1 according to the present embodiment, when switching to non-boosting mode during execution of boosting mode, voltage difference ΔVb between charge / discharge voltages of power storage units 6-1 and 6-2 is reduced. Thus, the voltage difference reduction control for controlling the voltage conversion operation in the converters 8-1 and 8-2 is executed. Then, converters 8-1 and 8-2 are switched to the non-boosting mode in response to voltage difference ΔVb of the charge / discharge voltage being reduced to a level at which overcurrent can be suppressed by voltage difference reduction control.

Hereinafter, voltage difference reduction control in converters 8-1, 8-2 will be described.
FIG. 6 is a diagram for describing the states of converters 8-1 and 8-2 in the voltage difference reduction control.

  Referring to FIG. 6, when charge / discharge voltage Vb2 of power storage unit 6-2 is higher than charge / discharge voltage Vb1 of power storage unit 6-1, converter ECU 2 keeps transistor Q2B on, thereby converting converter The boosting operation in 8-2 is stopped. On the other hand, converter ECU 2 generates switching command PWC1 for controlling the step-down operation for converter 8-1. Thereby, charging / discharging voltage Vb2 of power storage unit 6-2 is supplied to main positive bus MPL and main negative bus MNL via diode D2B of converter 8-2. The supplied charge / discharge voltage Vb2 of power storage unit 6-2 is stepped down in accordance with the on-duty of transistor Q1B of converter 8-1 and supplied to power storage unit 6-1.

  At this time, the average voltage of the DC power supplied from converter 8-1 to power storage unit 6-1 is a value obtained by multiplying DC voltage Vb2 between main positive bus MPL and main negative bus MNL by the on-duty of transistor Q1B. As a result, the voltage difference ΔVb of the charge / discharge voltage between power storage unit 6-1 and power storage unit 6-2 is reduced. Therefore, by gradually increasing the on-duty of transistor Q1B, voltage difference ΔVb can be reduced to a level at which overcurrent can be suppressed.

  FIG. 7 is a flowchart showing a control structure for realizing voltage difference reduction control in converter ECU 2.

  Referring to FIG. 7, when the process is started, control unit 22 (FIG. 3) performs switching for switching from the boost mode to the non-boost mode based on signal MD from mode determining unit 20 (FIG. 3). It is determined whether or not a request has occurred (step S11).

  When a request for switching to the non-boosting mode is generated (YES in step S11), control unit 22 stores power storage unit 6 from charge / discharge voltage detection units 12-1 and 12-2 (FIG. 1). Based on the charge / discharge voltage values Vb1 and Vb2 of −1 and 6-2, it is determined whether or not the voltage difference ΔVb (= | Vb1−Vb2 |) of the charge / discharge voltage value is larger than a predetermined reference voltage Vth ( Step S12). This predetermined reference voltage Vth passes overcurrent when power storage units 6-1 and 6-2 are completely connected in parallel to main positive bus MPL and main negative bus MNL (FIG. 5). Is set in advance to a voltage level capable of suppressing.

  When voltage difference ΔVb between the charge / discharge voltage values is equal to or lower than a predetermined reference voltage Vth (NO in step S12), control unit 22 controls converters 8-1, 8-2 to the non-boosting mode (step). S14). In this case, switching command generators 24 and 26 (FIG. 3) maintain transistors Q1B and Q2B of converters 8-1 and 8-2 on in accordance with signals CTL1 and CTL2 from controller 22, respectively.

  On the other hand, when voltage difference ΔVb of the charge / discharge voltage value is larger than predetermined reference voltage Vth (YES in step S12), control unit 22 further controls the charge / discharge voltage of power storage unit 6-1. It is determined whether or not value Vb1 is larger than charge / discharge voltage value Vb2 of power storage unit 6-2 (step S13).

  When charge / discharge voltage value Vb1 is equal to or lower than charge / discharge voltage value Vb2 (NO in step S13), control unit 22 maintains transistor Q2B of converter 8-2 on with respect to switching command generation unit 26. Signal CTL2 is output. On the other hand, control unit 22 outputs signal CTL1 for controlling the step-down operation of converter 8-1 to switching command generation unit 24 (step S15).

  On the other hand, when charge / discharge voltage value Vb1 is larger than charge / discharge voltage value Vb2 (YES in step S13), control unit 22 causes transistor Q1B of converter 8-1 to switch command generation unit 24. A signal CTL1 for maintaining on is output. On the other hand, control unit 22 outputs signal CTL2 for controlling the step-down operation of converter 8-2 to switching command generation unit 26 (step S16).

  FIG. 8 is a block diagram showing a control structure for realizing generation of a switching command in converter ECU 2. Since the switching command generator 24 and the switching command generator 26 shown in FIG. 3 have the same configuration and operation, FIG. 8 illustrates the control structure of the switching command generator 24 as an example.

  Referring to FIG. 8, switching command generation unit 24 includes a voltage command calculation unit 240, subtraction units 242 and 246, a proportional control unit (PI) 244, a selection unit 248, and a PWM signal conversion unit 250. .

Voltage command calculation unit 240 determines a target value (voltage target value) Vb1 ^* of charge / discharge voltage Vb1 of power storage unit 6-1. Specifically, when voltage command calculation unit 240 receives charge / discharge voltage values Vb1 and Vb2 from charge / discharge voltage detection units 12-1 and 12-2 (FIG. 1), voltage difference ΔVb (= | Vb1- Based on Vb2 |), a voltage target value Vb1 ^* is determined. At this time, voltage command calculation unit 240 gradually increases voltage target value Vb1 ^* with charge / discharge voltage Vb2 of power storage unit 8-2 as a final value.

Subtraction unit 242 calculates a voltage deviation from the difference between voltage target value Vb1 ^* and charge / discharge voltage Vb1 of power storage unit 6-1, and outputs the voltage deviation to proportional control unit (PI) 244. The proportional control unit 244 includes at least a proportional element (P) and an integral element (I), and outputs an operation signal corresponding to the input voltage deviation to the subtraction unit 246.

The subtracting unit 246 inverts the sign of the operation signal output from the proportional control unit 244, and adds the input / output voltage value Vh / voltage target value Vb1 ^* (reciprocal of the theoretical step-down ratio in the converter 8-1) to obtain a duty ratio. Command # Ton1B is output. This duty command # Ton1B is a control command that defines the on-duty of transistor Q1B (FIG. 2) of converter 8-1 in the step-down operation.

  The selection unit 248 receives the duty command # Ton1B and the value “1”, selects any one based on the signal CTL1 from the control unit 22 (FIG. 3), and outputs it to the PWM signal conversion unit 250 as the duty command Ton1B. To do. The value “1” is used to keep the duty command Ton1B “1”, that is, to keep the transistor Q1B of the converter 8-1 on when the converter 8-1 is selected to be in the control stop state.

  Specifically, selection unit 248 selects a value “1” when receiving signal CTL1 for maintaining transistor Q1B on from control unit 22, and controls step-down operation of converter 8-1 from control unit 22. When the signal CTL1 is received, the duty command # Ton1B is selected.

  The PWM signal conversion unit 250 compares the carrier wave (carrier wave) generated by the oscillation unit (not shown) with the duty command Ton1B to generate the switching command PWC1B.

  Further, PWM signal converter 250 uses duty command Ton1B to calculate duty command Ton1A (= 1-Ton1B) for defining the on-duty of transistor Q1A of converter 8-1. Then, the carrier wave (carrier wave) is compared with the duty command Ton1A to generate the switching command PWC1A.

  As described above, for converter 8-1, converter ECU 2 selects any one of the voltage control loop for charge / discharge voltage Vb1 of power storage unit 6-1 and “1” (control stop), and performs the step-down operation. A switching command PWC1 for control is generated.

  The functions of the block diagrams shown in FIGS. 3 and 8 may be configured in converter ECU 2 so as to include a circuit corresponding to each block. In many cases, however, converter ECU 2 has a processing routine according to a preset program. It is realized by executing.

Thus, when charge / discharge voltage Vb1 of power storage unit 6-1 is lower than charge / discharge voltage Vb2 of power storage unit 6-2, the voltage of the charge / discharge voltage is controlled by controlling the step-down operation in converter 8-1. The difference ΔVb can be reduced. In this step-down operation, voltage target value Vb1 ^* starts to rise from charge / discharge voltage Vb1 of power storage unit 6-1 with charge / discharge voltage Vb2 of power storage unit 6-2 as a final value.

However, when voltage target value Vb1 ^* becomes very close to charging / discharging voltage Vb2 of power storage unit 6-2, the on-duty of transistor Q1B of converter 8-1 becomes very large, for example, 0.98. Then, since the on-duty of 0.98 is eroded by dead time for preventing the transistors Q1A and Q1B from being turned on at the same time, it is not possible to secure a period during which the transistor Q1B should be turned on. In other words, in the on-duty of the transistor Q1B, in the region very close to 1.0, there is a problem that the original on-duty cannot be secured due to the dead time.

  Therefore, the voltage difference ΔVb of the charge / discharge voltage remains between the power storage units 6-1 and 6-2. Therefore, when the on-duty of transistor Q1B suddenly changes to 1.0 at the timing when the step-down operation is stopped, the charge / discharge voltage Vb1 of power storage unit 6-1 increases rapidly, thereby causing the power storage unit and the converter to become excessive. There is a risk of current passing.

Therefore, in this embodiment, when the on-duty of transistor Q1B calculated based on voltage target value Vb1 ^* in the step-down operation is affected by the dead time, switching commands PWC1A and PWC1B are performed according to the relationship shown in FIG. The frequency (hereinafter simply referred to as “carrier frequency”) fc of the carrier wave (carrier wave) used to generate the signal fc is reduced. According to this configuration, since the control cycle length determined by the carrier frequency fc is increased by lowering the carrier frequency fc, the ratio of dead time to the control cycle length is reduced to reduce the original on-duty. Can be secured.

  FIG. 9 is a diagram showing the relationship between the on-duty of transistor Q1B of converter 8-1 and carrier frequency fc.

  Referring to FIG. 9, when the carrier frequency fc is the predetermined frequency f1, the maximum on-duty value (hereinafter also referred to as the maximum on-duty) D_max1 of the transistor Q1B that is not affected by the dead time is the carrier frequency fc. Using the control cycle length T determined by (= f1) and the dead time Dt of the transistors Q1A and Q1B, the calculation can be performed by the equation (1).

D_max1 = (T−Dt) / T (1)
In Expression (1), T-Dt represents an effective control cycle length obtained by subtracting the dead time Dt from the control cycle length T.

That is, when the on-duty of the transistor Q1B calculated based on the voltage target value Vb1 ^* exceeds the maximum on-duty D_max1, the on-duty is affected by the dead time, so that the original on-duty is secured. It becomes impossible.

  On the other hand, in the region where the on-duty exceeds the maximum on-duty D_max1, the carrier frequency fc is changed so that the carrier frequency fc decreases as the on-duty increases. As a result, the control cycle length T in the above equation (1) becomes longer, so that the maximum on-duty can be substantially increased to approach 1.0.

  In the relationship shown in FIG. 9, the lower limit frequency f2 (<f1) is preset for the carrier frequency fc. This is effective to reduce the influence of the dead time as the carrier frequency fc is lower. On the other hand, when the current applied to the inductor L1 increases as the ON period of the transistor Q1A increases, the inductor L1. This is because the magnetic flux generated in the core of the core is saturated and the inductance of the inductor L1 is reduced. When the inductance of the inductor L1 is reduced, an excessive current passes through the converter 8-1, so that the original significance of performing the voltage difference reduction control (overcurrent prevention) is impaired. Therefore, the lower limit frequency f2 is set such that the current flowing through the inductor L1 has a current value that can maintain the core of the inductor L1 in the magnetization unsaturation.

  FIG. 10 is a timing chart of switching command PWC1 for controlling transistors Q1A and Q1B of converter 8-1.

  Referring to FIG. 10, when the step-down operation in converter 8-1 is started at timing t0, transistors Q1A and Q1B are turned on / off at a predetermined duty ratio in control cycle length T determined by carrier frequency fc (= f1). Turned off. In each control cycle length T, a dead time is provided to prevent the transistors Q1A and Q1B from being turned on simultaneously.

After timing t0, when voltage target value Vb1 ^* of converter 8-1 begins to rise from charging / discharging voltage Vb1 of power storage unit 6-1, on-duty of transistor Q1B also begins to increase. When the on-duty of transistor Q1B reaches maximum on-duty D_max1 at timing t1, converter ECU 2 lowers carrier frequency fc from predetermined frequency f1 according to the relationship between the on-duty of transistor Q1B and the carrier frequency shown in FIG. Let Thereby, after timing t1, the control cycle length starts to increase from the control cycle length T from timing t0 to timing t1.

  When the carrier frequency fc eventually reaches the lower limit frequency f2 in FIG. 9, the on-duty of the transistor Q1B is fixed at 1.0 at the timing t2.

  FIG. 11 is a timing chart of voltage difference ΔVb (= | Vb1−Vb2 |) between the on-duty of transistor Q1B of converter 8-1 and the charge / discharge voltage of power storage units 6-1, 6-2.

Referring to FIG. 11, when the step-down operation of converter 8-1 is started at timing t0, the on-duty of transistor Q1B increases as voltage target value Vb1 ^* increases as shown by line k1 in the figure. Increase. Thereby, as shown by line k3 in the figure, voltage difference ΔVb between power storage units 6-1 and 6-2 begins to decrease. Then, when the on-duty of the transistor Q1B reaches the maximum on-duty D_max1 at the timing t1, the carrier frequency fc starts to decrease from the predetermined frequency f1. Therefore, the on-duty of the transistor Q1B further increases from the maximum on-duty D_max1, and approaches 1.0. When the carrier frequency fc reaches the lower limit frequency f2 at the timing t2, the on-duty of the transistor Q1B is fixed to 1.0. At this time, since the charge / discharge voltage Vb1 of the power storage unit 6-1 has increased to a voltage level determined by the maximum on-duty D_max2 at the lower limit frequency f2, the voltage difference ΔVb between the power storage units 6-1 and 6-2 is The voltage difference ΔVb at the timing t1 is smaller. As a result, it is possible to reliably suppress an excessive current from passing when the step-down operation is stopped at the timing t2 and the mode is shifted to the non-step-up mode.

  For comparison, FIG. 11 shows a change in voltage difference ΔVb between power storage units 6-1 and 6-2 when the on-duty of transistor Q1B is fixed at 1.0 at timing t1. (See lines k3 and k4 in the figure). According to this, since the voltage difference ΔVb between the power storage units 6-1 and 6-2 is large, it is clear that an excessive current flows due to a rapid increase in the charge / discharge voltage Vb1 of the power storage unit 6-1.

  Thus, according to power supply system 1 according to the present embodiment, charging / discharging voltage between power storage units 6-1 and 6-2 when converters 8-1 and 8-2 are switched from the boosting mode to the non-boosting mode. It is possible to suppress an excessive current from passing through the system due to the difference ΔVb. As a result, the protection of the power supply system against an excessive current can be increased, and the overall energy efficiency can be further improved.

  FIG. 12 is a flowchart showing a control structure for realizing generation of a switching command in converter ECU 2. 12 is realized by the switching command generation unit 24 (FIG. 3) functioning as each control block shown in FIG.

Referring to FIG. 12, when the process is started, switching command generation unit 24 sets voltage target value Vb1 ^* of charge / discharge voltage Vb1 of power storage unit 6-1 (step S21). Furthermore, the first switching command generator 24 calculates the duty command # Ton1B of the transistor Q1B of the converter 8-1 based on the set voltage target value Vb1 ^* (step S22).

  Next, switching command generation unit 24 determines whether or not signal CTL1 for controlling the step-down operation of converter 8-1 is received from control unit 22 (step S23).

  When signal CTL1 for controlling the step-down operation of converter 8-1 is received from control unit 22 (YES in step S23), switching command generation unit 24 uses duty cycle Ton1B of transistor Q1B as the duty command Ton1B. Command # Ton1B is selected (step S24).

  On the other hand, when signal CTL1 for controlling the step-down operation of converter 8-1 is not received from control unit 22, that is, when signal CTL1 for maintaining transistor Q1B on is received from control unit 22 (step In the case of NO in S23, the switching command generator 24 selects the value “1” as the duty command Ton1B of the transistor Q1B (step S25).

  Then, the switching command generator 24 sets the carrier frequency fc based on the duty command Ton1B (step S26). Specifically, the switching command generator 24 stores the relationship between the on-duty of the transistor Q1B and the carrier frequency fc in FIG. 9 in advance as a carrier frequency setting map, and when the duty command Ton1B is set, The corresponding carrier frequency fc is extracted from the carrier frequency setting map.

  Finally, the switching command generator 24 compares the carrier wave having the set carrier frequency fc with the duty command Ton1B to generate the switching command PWC1B. In addition, switching command generation unit 24 uses duty command Ton1B to calculate duty command Ton1A (= 1-Ton1B) for defining the on-duty of transistor Q1A of converter 8-1. Then, the carrier wave is compared with the duty command Ton1A to generate the switching command PWC1A (step S27).

  Note that switching commands PWC2A and PWC2B are also generated for the switching command generator 26 (FIG. 3) according to the same control structure as the switching command generator 24 described above. Therefore, detailed description thereof will not be repeated.

  In the embodiment of the present invention, driving force generator 3 corresponds to a “load device”, main positive bus MPL and main negative bus MNL correspond to “power line pairs”, and converters 8-1 and 8-2 This corresponds to “a plurality of voltage conversion units”. And converter ECU2 implement | achieves a "control apparatus."

  In the embodiment of the present invention, the power supply system is configured to include two converters and a power storage unit. However, even in the case of three or more converters and power storage units, the non-boosting mode In response to receiving a request for switching to the power supply, the converter corresponding to the power storage unit having a relatively high charge / discharge voltage is stopped while the converter corresponding to the power storage unit having a relatively low charge / discharge voltage is stepped down. By executing the above, it is possible to exhibit the same effect as described above. That is, it is possible to improve the overall energy efficiency while suppressing an excessive current from passing through the plurality of power storage units and the converter constituting the power supply system.

  Further, in the embodiment of the present invention, the configuration using the driving force generation unit including two motor generators as an example of the load device has been described, but the number of motor generators is not limited. Furthermore, the load device is not limited to the driving force generation unit that generates the driving force of the vehicle, and can be applied to a load that consumes electric power.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a schematic configuration diagram showing a main part of a vehicle including a power supply system according to an embodiment of the present invention. 1 is a schematic configuration diagram of a converter according to an embodiment of the present invention. It is a block diagram for implement | achieving the production | generation of the switching command (step-up operation | movement) in converter ECU. It is a flowchart for demonstrating the determination operation | movement of the control mode of the converter in converter ECU. It is a figure for demonstrating the state of the converter in non-boosting mode. It is a figure for demonstrating the state of the converter in voltage difference reduction control. It is a flowchart which shows the control structure for implement | achieving the voltage difference reduction control in converter ECU. It is a block diagram which shows the control structure for implement | achieving the production | generation of the switching command in converter ECU. It is a figure which shows the relationship between the on-duty of the transistor of a converter, and a carrier frequency. It is a timing chart of the switching command which controls the transistor of a converter. It is a timing chart of the voltage difference of the on-duty of the transistor of a converter, and the charging / discharging voltage of an electrical storage part. It is a flowchart which shows the control structure for implement | achieving the production | generation of the switching command in converter ECU.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Power supply system, 2 Converter ECU, 3 Driving force generation part, 4 Battery ECU, 6-1, 6-2 Power storage part, 8-1, 8-2 Converter, 10-1, 10-2 Charge / discharge current detection part, 12-1, 12-2 Charge / Discharge Voltage Detection Unit, 14-1, 14-2 Temperature Detection Unit, 16 Input / Output Current Detection Unit, 18 Input / Output Voltage Detection Unit, 20 Mode Determination Unit, 22 Control Unit, 24, 26 Switching command generator, 30-1, 30-2 inverter, 32 drive ECU, 34-1, 34-2 motor generator, 36 power transmission mechanism, 38 drive shaft, 40-1, 40-2 chopper circuit, 100 vehicle, 240 voltage command calculation unit, 242, 246 subtraction unit, 244 proportional control unit, 248 selection unit, 250 PWM signal conversion unit, C, C1, C2 smoothing capacitor, D1A, D1B, D A, D2B diode, L1, L2 inductor, LN1A, LN2A positive line, LN1B, LN2B wiring, LN1C, LN2C negative bus, MNL main negative bus, MPL main positive bus, Q1A, Q1B, Q2A, Q2B transistor.

Claims (5)

A power supply system including a plurality of power storage units each configured to be chargeable / dischargeable,
A pair of power lines configured to be able to transfer power between a load device and the power supply system;
A plurality of voltage conversion units provided between the plurality of power storage units and the power line pair, each performing a voltage conversion operation between the corresponding power storage unit and the power line pair;
A control device for controlling a voltage conversion operation in the plurality of voltage conversion units,
Each of the plurality of voltage conversion units includes first and second switching elements connected in series between the power line pair, and performs a voltage conversion operation by a switching operation of the first and second switching elements,
The controller is
A first control mode for controlling the plurality of voltage conversion units such that each of the plurality of voltage conversion units stops a voltage conversion operation; and at least one of the plurality of voltage conversion units performs a voltage conversion operation. Mode setting means for setting to any one of the second control modes to be controlled;
When the plurality of voltage conversion units set in the second control mode are switched to the first control mode by the mode setting means, the voltage difference of the charge / discharge voltage between the plurality of power storage units A voltage conversion control means for stopping the voltage conversion operation in the plurality of voltage conversion units according to the fact that is below a predetermined reference value,
The voltage conversion control means includes
When the voltage difference is equal to or greater than the predetermined reference value, a voltage from the first power storage unit having a relatively high charge / discharge voltage among the plurality of power storage units is directly output to the power line pair. Thus, the voltage conversion operation in the corresponding voltage conversion unit is stopped, and the second power storage unit having a relatively low charge / discharge voltage among the plurality of power storage units is charged with the voltage from the first power storage unit. Voltage difference reducing means for controlling the step-down operation in the corresponding voltage conversion unit,
The voltage difference reducing means is
In the voltage conversion unit corresponding to the second power storage unit, the carrier frequency for controlling the switching operation of the first and second switching elements is set to the first frequency and is determined by the first frequency. First switching command generation means for increasing a first on-duty that is a ratio of a control cycle length and an on-period length of the first switching element;
A value obtained by subtracting an effective control cycle length obtained by subtracting a dead time during which both the first and second switching elements are turned off from the control cycle length is divided by the control cycle length is set in advance as a maximum on-duty, and the first And a second switching command generation unit that lowers the carrier frequency from the first frequency when the first on-duty reaches the maximum on-duty in one switching command generation unit. . Each of the plurality of voltage conversion units further includes an inductor connected to a connection point between the first switching element and the second switching element,
The second switching command generation means lowers the carrier frequency using a second frequency lower than the first frequency as a lower limit frequency,
2. The power supply system according to claim 1, wherein the second frequency is set such that a current flowing through the inductor has a current value capable of maintaining the core of the inductor in a magnetization unsaturated state.   3. The power supply system according to claim 2, wherein the mode setting unit sets the plurality of voltage conversion units to the first control mode when a required power of the load device with respect to the power supply system is lower than a predetermined threshold value. The load device includes a driving force generation unit that receives electric power supplied from the power supply system via the power line pair and generates driving force of the vehicle,
The power supply system according to claim 2, wherein the mode setting means sets the plurality of voltage converters to the first control mode when the vehicle is in a stopped state. A power supply system including a plurality of power storage units each configured to be chargeable / dischargeable;
A vehicle including a driving force generator that receives electric power supplied from the power supply system and generates a driving force;
The power supply system includes:
A pair of power lines configured to be able to exchange power between the driving force generator and the power supply system;
A plurality of voltage conversion units provided between the plurality of power storage units and the power line pair, each performing a voltage conversion operation between the corresponding power storage unit and the power line pair;
A control device for controlling a voltage conversion operation in the plurality of voltage conversion units,
Each of the plurality of voltage conversion units includes first and second switching elements connected in series between the power line pair, and performs a voltage conversion operation by a switching operation of the first and second switching elements,
The controller is
A first control mode for controlling the plurality of voltage conversion units such that each of the plurality of voltage conversion units stops a voltage conversion operation; and at least one of the plurality of voltage conversion units performs a voltage conversion operation. Mode setting means for setting to any one of the second control modes to be controlled;
When the plurality of voltage conversion units set in the second control mode are switched to the first control mode by the mode setting means, the voltage difference of the charge / discharge voltage between the plurality of power storage units A voltage conversion control means for stopping the voltage conversion operation in the plurality of voltage conversion units according to the fact that is below a predetermined reference value,
The voltage conversion control means includes
When the voltage difference is equal to or greater than the predetermined reference value, a voltage from the first power storage unit having a relatively high charge / discharge voltage among the plurality of power storage units is directly output to the power line pair. Thus, the voltage conversion operation in the corresponding voltage conversion unit is stopped, and the second power storage unit having a relatively low charge / discharge voltage among the plurality of power storage units is charged with the voltage from the first power storage unit. Voltage difference reducing means for controlling the step-down operation in the corresponding voltage conversion unit,
The voltage difference reducing means is
In the voltage conversion unit corresponding to the second power storage unit, the carrier frequency for controlling the switching operation of the first and second switching elements is set to the first frequency and is determined by the first frequency. First switching command generation means for increasing a first on-duty that is a ratio of a control cycle length and an on-period length of the first switching element;
A value obtained by subtracting an effective control cycle length obtained by subtracting a dead time during which both the first and second switching elements are turned off from the control cycle length is divided by the control cycle length is set in advance as a maximum on-duty, and the first And a second switching command generation unit configured to lower the carrier frequency from the first frequency when the first on-duty reaches the maximum on-duty in one switching command generation unit.

Images